Over the past decade, there has been a concerted effort to reduce atmospheric pollution caused by volatile solvents which are emitted during the painting process. However, it is often difficult to achieve high quality, smooth coating finishes, such as are required in the automotive industry, without using organic solvents which contribute greatly to flow and leveling of a coating.
One of the major goals of the coatings industry is to minimize the use of organic solvents by formulating waterborne coating compositions which provide a smooth, high gloss appearance, as well as good physical properties including resistance to acid rain. Unfortunately, many waterborne coating compositions do not provide acceptable appearance. A particularly acute problem is cratering or the development of small depressions in the surface of the coating. One solution to the cratering problem is to eliminate sources of contaminates in the coatings. However, it is generally impractical to eliminate sources of contamination in an industrial setting. Other coating appearance problems can be attributed to poor flow and leveling.
Another challenge to formulators of waterborne coatings is to provide good acid resistance, particularly battery acid resistance, while maintaining acceptable physical properties. Lack of humidity resistance or blushing is another problem facing waterborne coating formulators.
Therefore, it would be desirable to provide a waterborne coating composition which is useful as an original finish for automobiles and which can be applied as a smooth, acid resistant film under a variety of conditions with minimal cratering or blushing.